1. Field of the Invention
The present invention relates to pipeline repairing techniques, and more particularly to a method of everting or inserting a pipe liner bag inside out into a pipeline using a fluid pressure in a pipeline lining operation.
2. Description of the Related Art
When an underground pipeline, such as pipelines and passageways, becomes defective or too old to perform properly, the pipeline is repaired and rehabilitated without digging the earth to expose the pipeline and disassembling the sections of the pipeline. This non-digging method of repairing an underground pipeline has been known and practiced commonly in the field of civil engineering. The pipeline lining method utilizes a tubular pipe liner bag made of a resin absorbent material impregnated with a hardenable resin, and having the outer surface covered with a highly air-tight plastic film. The tubular pipe liner bag is inserted into a pipeline to be repaired by means of a pressurized fluid such that the pipe liner bag is turned inside out as it proceeds deeper in the pipeline. Hereinafter, this manner of insertion shall be called "everting". When the entire length of the tubular liner bag is everted(i.e., turned inside out) into the pipeline, the everted tubular liner is pressed against the inner wall of the pipeline by a pressurized fluid, and the tubular flexible liner is hardened as the hardenable resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag. It is thus possible to line the inner wall of the defective or old pipeline with a rigid liner without digging the ground and disassembling the pipeline sections.
When a pipe liner bag is everted into a pipeline by a pressure of compressed air in the pipeline lining operation as mentioned above, an uneverted portion of the pipe liner bag is extended over an already everted portion of the same in the pipeline, so that a large friction force occurs between the two pipe liner bag portions, thus presenting a problem that a smooth eversion of the pipe liner bag is prevented by the friction force.
To cope with this problem, Japanese Patent Publication No. 63-11134 has proposed a method of injecting a lubricant such as oil into a pipe liner bag which has already been everted in a pipeline.
However, in the proposed method, a large amount of lubricant must be injected into a pipe liner bag for uniformly applying the lubricant over the surface thereof. In addition, when an excessive amount of lubricant is applied on the pipe liner bag, a laborious and time consuming post-treatment is required for removing the lubricant. Particularly, when water pressure is used for the eversion of the pipe liner bag, or when hot water is used for heating a hardenable resin impregnated in the pipe liner bag, the lubricant such as oil is mixed with water. Since the water mixed with oil may not be wasted as it is, a costly and time consuming post-treatment must be performed to remove the lubricant.
Also, although a lubricant may be previously applied over the entire surface of an uneverted pipe liner bag, this is also a laborious and time consuming operation.